Pathogens: bacteria

4. Bacteria are living cells and, in favourable conditions, can multiply rapidly. Once inside the body, they release poisons or toxins that make us feel ill

2 of 8

Pathogens: viruses

Viruses are many times smaller than bacteria. They are among the smallest organisms known and consist of a fragment of genetic material inside a protective protein coat.

Viruses can only reproduce inside host cells and they damage the cell when they do this. A virus can get inside a cell and, once there, take over and make hundreds of thousands of copies of itself. Eventually the virus copies fill the whole host cell and burst it open. The viruses are then passed out in the bloodstream, the airways, or by other routes.

Diseases caused by viruses include:

influenza (flu)

colds

measles

mumps

rubella

3 of 8

White blood cells

White blood cells

A white blood cell ingesting disease-causing bacteria.

White blood cells can:

ingest pathogens and destroy them

produce antibodies to destroy particular pathogens

produce antitoxins that counteract the toxins released by pathogens.

4 of 8

Vaccinations-

Vaccination causes the body to produce enough white blood cells to protect itself against a pathogen. Antibiotics are effective against bacteria, but not against viruses. Some strains of bacteria are resistant to antibiotics. So people can be immunised against a pathogen through vaccination. Different vaccines are needed for different pathogens. For example, the MMR vaccine is used to protect children against measles, mumps and rubella.

Vaccines can contain:

live pathogens treated to make them harmless

harmless fragments of the pathogen

dead pathogens.

5 of 8

Vaccacinations- Advantages and disadvantages

Advantages:

High probility of being immune to diseases- If you do contact with the disease again it will be much milder and less threatening form.

Much cheaper than being treated or hospilatilized.

Disadvantages:

After getting the injection you could feel fore for couple of days.

Some people may be allergic to the components of the vaccination.

6 of 8

Medicines

Some medicines help to relieve the symptoms of a disease while others kill the infectious pathogens.

Painkillers

Painkillers like paracetamol and aspirin are available 'over-the-counter' at pharmacies.

Painkillers helps to relieve the symptoms of an infectious disease, but they do not kill the pathogens involved. For example, paracetamol, aspirin and morphine block nerve impulses from the painful part of the body, or block nerve impulses travelling to the part of the brain responsible for perceiving pain.

7 of 8

Medicines- Antibotics

Some medicines help to relieve the symptoms of a disease while others kill the infectious pathogens.

Antibiotics

A bacterium damaged and distorted by penicillin

Antibiotics are substances that kill bacteria or stop their growth. They do not work against viruses because they live and reproduce inside cells. It is difficult to develop drugs that kill viruses without also damaging the body’s tissues.